Seal for electric lamps and similar devices



Oct. 15, 1946.

Fig.1.

E. KETTLEWELL SEAL FOR ELECTRIC LAMPS AND SIMILAR DEVICES Filed March 50, 1944 Inventor: Eric e't't'LeweLL,

' His Ak't'orneg.

Patented Got. 15, 1946 SEAL FOR ELECTRIC LAMPS AND SIIVIILAR DEVICES Eric Kettlewell, Kingsbury, London, England, as

signor to General Electric Company, a corporation of New York Application March'30, 1944, Serial No. 528,661 In Great Britain April 3, 1942 This invention relates to devices of a type comprising an envelope of quartz or similar refractory or vitreous material with an electrode therein and means of current lead connection to the exterior sealed through a part of the envelope structure. -The invention involves novelty in methods of manufacture, as well as in construction. The invention is especially applicable to 2 Claims. (of. 49-925) high pressure metal vapor discharge devices, in-

eluding mercur vapor lamps which in operation dissipate power considerably exceeding 1 kw.

The current connections of such discharge devices are usually carried through the quartz or other vitreous envelopes by means of strip-form lead seals, comprising strips of sheet metal (often so thin as to be quite properly termed foil) embedded in the vitreous material while it is softened or fused by heat. Besides the delicacy or difllculty of making such joints, there is the problem of making satisfactory electrical and mechanical connection between the thin strips and the electrode member to which they lead, particularly when this member is relatively massive, as well as of firmly supporting the member.

It is an aim of this invention to overcome such difilculties by improved constructions and methods. Various other features and advantages of the invention will appear from the following description of a species or form of embodiment and. a mode of fabrication, and from the drawing.

In manufacturing a quartz envelope device in accordance with the invention, in the form hereinafter described, (1) a part of a refractory metal electrode member (preferably cylindrical) is wrapped with thin refractory sheet metal or foil, which is welded to the electrode at a plurality of places, (2) thin strips of refractory sheet metal or foil adapted for a strip seal are attached and electrically connected to the wrapping, and thus to the electrode, (3) the electrode and a quartz core in line with it are placed within a quartz tube or sleeve with the metal strips extending outward along the core, between the same and said tube, and (4) the said tube (or part of it) is collapsed upon the enclosed core and strips, and even on the foil-enveloped portion of the electrode. In this procedure, the order or distinction of steps (1) and (2) is immaterial, and uniting the strips and the electrode wrapping may be understood to include an original integral union left unsevered: for example, the foil wrapping and the strips may be cut out of the same sheet of metal in one piece and part of this piece wrapped around the electrode end, leaving the strips projecting therefrom as tags or streamers, the wrapped portion being welded to the electrode. And with respect to steps (3) and (4), it is desirable, in the case of a relatively massive electrode member, that the quartz core have substantially the same external shape of cross-section as the adjacent end portion of the electrode-for instance, if the electrode is a cylindrical rod, the core may be a rod or tube of about the same external diameter-and-that the quartz sleeve should be collapsed upon most or all the wrapped part of the electrode. It is generally undesirable to collapse quartz upon the unwrapped part of the electrode.

By way of example, one embodiment of the invention will now be described with reference to the accompanying drawing, in which:

,Fig. 1 is a perspective or tilted side view of an electrode assembly constructed as above indicated; Fig. 2 is a side view of a complete discharge device embodying this electrode; Fig. 3 is a fragmentary, sectioned elevation of the electrode assembly; and Fig. 4 is a perspective view of a modification of the foil lead-in conductor.

In Fig. l, a relatively massive refractory metal electrode of a high pressure metal vapor electric lamp is shown as a tungsten rod or cylinder I, which may be 30 mm. long and 7 /2 mm. in diameter, for example. Refractory sheet metal or foil for the electrode wrapping and the seal strips may consist of molybdenum sheet 0.015 mm. thick. A band 2 of this foi1 (15 mm. wide, for example) is wrapped around one end of the electrode member I and welded to it. Two strips 3, 3 of the sheet molybdenum (each 10 mm. wide and 40 mm. long, for example) are each welded at one end to the wrapping 2, while at the other end each strip is welded to a stout external wire lead 4, which may be multistranded as shown. Using a cylindrical quartz rod (also 7 /2 mm. in diameter) as the core 5 in alignment with the electrode rod l-and as shown forming as it were a prolongation of the electrode-the lead strips 3, 3 and the core 5 are both inserted or fitted into a quartz tube or sleeve 6 (of suitable internal bore), so that the strips lie between the core and the tube, the wrapped end of the electrode I being also inserted or fitted into the end of the tube. The tube or sleeve 6 is collapsed, by heating and softening it, over the whole distance from the boundary between the wrapped and unwrapped portions of the electrode l to slightly beyond the junction of strips 3, 3 and leads 4, 4, and is interfused and sealed with the core 5 within it.

Assuming the tube or sleeve 6 to be itself the the seal between the plug sleeve and its core' 5.

Thereafter the plug with the electrode! carried thereby is inserted into a neck or sleeve portion In of a vitreous refractory lampenvelope ll,,so that the electrode I is exposed in 'the'envelope,

and the envelope neck l0 is'softened and col-f lapsed on the plug by heat and interfused with it, thus sealing the plug into, the;.ne'ck,.allaasindicated in Fig. 2.

Fig. 4 shows a modification of the foil lead-in conductor wherein the wrapped portion 2 and the ribbons or streamers 3' (corresponding to the portions 2 and 3 in Fig. 3) are cut out of'the same sheet of metal in one piece.

In general, as. a practical matter, :refractory envelope material similar to quartz includes any highly silicious vitreous material which'has a coeflicient of expansion of not more substantially than 1L5 per degree centigradeas comp "with a correspondingcoeflicient of expansioniof 055x10 per degree centigrade for-fused quartz 'or quartz glass itself.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In a. seal of the class described, the combination of a metallic rod-like electrode and a core member of vitreous material of substantially the same diameter aligned in abutting end-to-end relation,,a metallic, foil conductor including a portion wrapped around the end of said electrode adjacent said core member and another portion extending therefrom longitudinally of said core .1 member," and asleeve of vitreous material fused around said core member and the portion of said v.electrodewhich iswrapped with foil, said foil .;conductor.,being. embedded in the fused seal.

.;2.-In;-aseal of, the class described, the combination of a metallic rod-like electrode and a core member-of vitreous material of substantially the same diameter aligned in abutting end-to-end relation, a metallic foil conductor including a portion wrapped around the end of said electrode adjacent said core member and .a plurality of ribbon portions'extending therefrom longitudinally of said core member, and a sleeve of vitreous material fused around said core member ,and the portion of' said electrode which is wrapped with foil, said foil conductor being embedded in the fused seal.

ERIC KE'I'ILEWELL. 

